BK7 is an optical material used in a large fraction of EKSMA OPTICS products. It is relatively hard glass, doesn’t scratch easily and can be handled without special precautions. The inclusion and bubble content of BK7 is very low: cross-section totally less than 0.03 mm2 per 100 cm3. Another important feature of BK7 is its excellent transmission down to 350 nm. Due to these properties, including inexpensiveness, BK7 is used widely throughout the optics industry.